xSrTiO_3-(1-x)LaAlO_3介电陶瓷的结构和介电性能

xStructure and Dielectric Properties of xSrTiO_3-(1-x)LaAlO_3 Dielectric Ceramics

采用固相反应法制备了xSrTiO3-(1-x)LaAlO3(x=0.4～0.7)介电陶瓷,分析了不同x值陶瓷的结构和介电性能。结果表明:该陶瓷主相为钙钛矿固溶体,x=0.4～0.5时,为正交钙钛矿结构,在x=0.55～0.7时,为赝立方钙钛矿结构;赝立方结构的陶瓷具有较高的介电常数(ε>50)和低介电损耗(10-3～10-4)及近零的温度系数;陶瓷从赝立方结构转变成正交结构时,介电常数明显下降(ε=34～45),介电损耗迅速增大(约10-2);x=0.6,0.7的陶瓷具有优良的介电性能,ε>55,tanδ在10-3～10-4之间(f=1MHz);x=0.4时陶瓷具有优异的微波介电性能,ε=30.5,Qf=40 177GHz,τf=-22.9×10-6℃-1。

xSrTiO3-（1-x）LaAlO3（x=0.4-0.7 dielectric ceramics were prepared by solid state reaction method, the structure and properties of ceramics with different x value were discussed. The results show that perovskite solid solution was the main phase of this ceramics. The perovskite were orthogonal structure and constrain cubic structure when x were 0. 4--0. 5 and 0. 55--0. 7 respectively. The ceramics with the pseudocubic structure exhibited the higher dielectric constant （ε〉 50）, lower dielectric loss （10 3_ 10-4）and near-zero temperature coefficient. The dielectric constant decreased obviously （ε= 35--45） and dielectric loss increased rapidly （about 10.2） when the ceramics transformed from orthogonai structure to the constrain cubic structure. Good dielectric properties （ε）55, tan 3 of the ceramics was about 10 -3- 10-4 at 1 MHz）were achieved when x was 0.6 and 0. 7. Excellent microwave dielectric properties of ceramic （x=0. 4） were achieved as following： ε=30.5,Qf=40177GHz,rf=-22.9×10^-6℃-1.